1. Field of the Invention
The invention relates generally to automatic calibration circuits. More particularly the invention relates to a method and apparatus for automatically calibrating the output of a plurality of pressure transducers used in a hydromechanical gear shaping machine.
2. Description of the Prior Art
Hydraulic pressure transducers are used in hydromechanical gear shaping machines such as shown in U.S. Pat. Nos. 4,125,056, 4,136,302 and 4,254,690. Each of these patents has been assigned to the assignee of the present invention and is incorporated by reference herein. These pressure transducers generate analog electrical signals which are proportional to their associated hydraulic pressure levels. Proper operation of the hydromechanical gear shaper is highly dependent upon the proper operation of these transducers and the precise measurement of the load pressure and supply pressure.
It has been found that the pressure transducers used in prior art hydromechanical gear shaping machines have, after repeated operation tended to drift so that the electrical outputs of the sensors and their associated circuit components drifted as a result of amplifier gain or voltage offset changes. Such deviations are obviously detrimental to the proper operation of the machine and necessitate recalibration or replacement of the error producing components. Additionally, the inaccuracies of the sensor output may lead to operating inefficiencies if the signals indicate that greater power is required then is actually necessary for the proper performance of the gear shaper.
Accordingly, it is an object of this invention to overcome the disadvantages associated with these prior art pressure transducers by providing an automatic calibration means for compensating for detected errors. It is another object of this invention to produce such an automatic calibration means for periodically compensating for detected errors. It is also an object of this invention to avoid the necessity of precisely adjusting the initial values of various components associated with the transducer circuits.